Altruism, compassion, empathy, love, conscience, the sense of justice—all of these things, the things that hold society together, the things that allow our species to think so highly of itself, can now confidently be said to have a firm genetic basis. That’s the good news. The bad news is that, although these things are in some ways blessings for humanity as a whole, they didn’t evolve for the “good of the species” and aren’t reliably employed to that end. Quite the contrary: it is now clearer than ever how (and precisely why) the moral sentiments are used with brutal flexibility, switched on and off in keeping with self-interest; and how naturally oblivious we often are to this switching. In the new view, human beings are a species splendid in their array of moral equipment, tragic in their propensity to misuse it, and pathetic in their constitutional ignorance of the misuse.
– Robert Wright, The Moral Animal (1994)